OLAP

V. SaranyaAP/CSE

Sri Vidya college of Engineering & Technology, Virudhunagar

Need for OLAP

• Business problems need query centric db.• Need multidimensional approach.Characteristics of above problems: Extract large number of records from large

data set. Data summary.

To solve these kind of problems we need OLAP

Introduction to OLAP

• Continuous iterative process.• Operations are:– Drill down– Drill up– pivot

Multidimensional data model

• How many students done the exams conducted by department in college.

• Dimensions are:– Students– Exams– Department– College.

Response time of multidimensional query depends upon the number of cells to be added on the fly.Number of dimension increases=no of cube cell increase

Data Cubes

OLAP Guidelines• Multidimensional conceptual view• Transparency• Accessibility• Consistent reporting performance• Client/Server architecture• Generic dimensionality• Dynamic square matrix handling• Multiuser support• Unrestricted cross dimensional operation• Institutive data manipulation• Flexible reporting• Unlimited dimension and aggregation levels

• Comprehensive database management tools• The ability to drill down to detail view• Incremental database refresh• SQL interface.

Classification of OLAP tools

• Based on multidimensional db.• Allow the users to analyze the data using

views.• Need MDDB.• Classifications:– MOLAP– ROLAP

M(Multidimensional)OLAP

• Uses MDDBMS to organize and navigate data• Data Structure: Array• Segregate the OLAP thro APIPros:Excellent performanceResponse time.Cons:Series analysis iteration

Example

Organization tool• Arbor software: ESSbase• Oracle: Express server• Pilot Software: Light Slip Server• Snipper: TM/I• Planning Science: Gentium• Kenan technology: Multiway

Challenges• Data structure to support multiple subject area of data.• Analyze which data can be navigated and analyzed.• When the navigation changes the data structure needs to be

physically reorganized.• Need different skill set and tools for DBA to build, maintain

database.• Need hybrid solution.

Hybrid Solution:Integration of multidimensional data storage with RDBMS,Provide users with MDDSData maintained in RDBMS.

MOLAP Architecture

Database Server

Meta Data Request

Processing

MOLAP Server

Load

Result

SQLFront End Tool

Result Set

InfoRequest

• This allows the MDDS to dynamically obtain the detail maintained in RDBMS when the application reaches the bottom of multidimensional cells during drill down analysis.

• Best for Sensitive applications.

ROLAP• Fastest growing style of OLAP• Products of ROLAP have been engineered to

support products directly through meta data.• Enables multi dimensional views of 2D

relational tables.• Pros:– Flexibility

• Cons:– Data base design

ROLAP

Database Server

Meta Data Request

Processing

ROLAP Server

Resultset

SQLFront End Tool

Result Set

InfoRequest

Vendors Tools• Information advantage Axsys• Microstrategy Dss agent/ Dss server• Platinum/Prodea software Beacon• Sybase High gate project

Managed Query Environment/HOLAP

• Provides user with ability to perform limited analysis capability either directly with RDBMS products or

• Intermediate MOLAP.• The ad hoc query converted to provide data cube.Done by:1. Convert the query to select data from DBMS2. Deliver the data to desktop where it is placed in data

cube.3. Data cube is stored locally to reduce overhead of

creation of the cube.4. Now user can perform multi dimensional analysis.

HOLAP/MQE/Hybrid architecture

RDBMS

Database Server

MOLAP Server

Resultset

SQL

Front End Tool

Result Set

InfoRequest

LoadResult set OR

SQL Query

• Pros:– Simple installation– Administration is easy– Network traffic is less

• Cons:– Redundancy– Inconsistency.

OLAP tools and Internet• Internet free resource, provides connectivity, can do

complex administration jobs, store and manage data applications

• Data warehousingGeneral features of web enabled data access:• 1st generation websites:– Static distribution model– Client access static html pages via browser.– Decision support reports stored as html doc and delivered to

users.

• Deficiencies:– Interaction with clients.

• 2nd generation:– Supports interaction– Multi tiered architecture– Client submits the query in html to web server– Server transform the request to CGI– The gateway submits SQL queries to db and

receives and translates to html and sends to page requester.

Web Processing Model